This patch allows AC_INIT to properly set the PACKAGE variables in the
Makefiles. In turn, this allows docdir use to work correctly. With
the new behaviour, things placed in docdir go to share/doc/bacula.
Previously the would end up in share/doc.
We move the detection of the source directory to a separate
AC_CONFIG_SRCDIR macro call.
Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>